Recording VST automation into an existing midi recording

I recorded the notes of the bassline i created in my VST in one take, and then in a 2nd recording i tweaked a dial that i had mapped to filter cutoff.

I 'assumed' that the CC data would be merged into the existing midi region that i recorded in the first take, but it wasnt. It appears to have overlapped the first take and now no notes play. As you can see in the screenshot, i started playing with the filter cutoff after the 3rd bar...

Can this automation data be merged in? If not, how do i do a retake, and get it to merge in while recording?